came up during the BEP029 (motion) community review:

• [ENH] Extend BIDS for Motion data (BEP029) #981 (comment)

also related to:

• [SCHEMA] Refactor channel types #1126
• Support full object definitions for valid values in schema #904

Some BIDS modalities allow for channels.tsv metadata:

• EEG
• MEG
• iEEG
• NIRS

channels.tsv files MUST have a type column that contains (upper case) strings from a defined vocabulary as specified in the modality specific sections. This column MUST be the second column in channels.tsv files.

In the schema, the valid values for type are specified separately for EEG, MEG, iEEG, and NIRS, see:

Even though in the spec, it says:

For EEG (types are shared with MEG and iEEG):

For MEG (no mention of sharing):

For iEEG (types are shared with MEG and EEG):

For NIRS (types are shared with EEG, MEG, and iEEG -- see last sentence):

We should:

1. clarify/formalize how channel types may be shared between modalities
2. think about how to make this clearer in the schema and the associated rendering of channel type tables in the modality sections

I propose that channel types should be shared between all BIDS modalities.